Since a hand-over greatly affects a communication quality in a mobile communication system in which a user moves, it is preferable to estimate and to acquire an area in which the hand-over is carried out (hereinafter, referred to as hand-over area) in design and operation. When the hand-over area becomes apparent, it is possible to make a design in which a hand-over occurs less frequently and to determine a failure caused by a hand-over in operation.
Exemplified as a conventional hand-over estimation method is “AirMagnet Surveyor (http://www.toyo.co.jp/wlan/d_airmagnet_sv.html, http://www.airmagnet.com/)” which is a commercially available site survey tool. The tool displays the receiving powers in respective points on a screen in colors (using different colors in respective contours) based on an estimation carried out by actually measuring the received power from a base station in wireless LAN. As one of the functions of the tool, there is provided a function for displaying an area, in which areas covered by a plurality of base stations overlap, as a hand-over area.
In contrast, an actual hand-over processing is carried out when two conditions, that is, a condition that the received signal quality from an associated base station is equal to or less than a prescribed value (shown by Qth) and a condition that a difference between the received signal quality of a destination base station and the received signal quality of the associated base station is equal to or more than a prescribed value (shown by h). Exemplified, as examples of the received signal quality are received power, delay spread, SNR (signal-to-noise power ratio), SIR (signal-to-interference noise power ratio), transmission loss, error rate (bit error rate and block error rate), and the like. It is also possible to use one or a plurality of combinations of them.
Accordingly, a terminal in transit monitors the received signal quality of an associated base station and the received signal quality of the base station having the best received signal quality in the base stations other than the associated base station, and carries out a hand-over processing at the time the above conditions are achieved. However, the area including the overlapping covered areas which is provided by the site survey tool is an area in which both the received signal quality of the associated base station and the received signal qualities of the other base stations are better than a prescribed quality and is different from an area shown by the above conditions. That is, since an actual hand-over is determined from a difference between the received signal quality of an associated base station and the received signal quality of a hand-over destination base station and carried out when a hand-over achieving condition changes, an area, in which covered areas simply overlap, does not agree with a hand-over area.
Note that Patent Documents 1, 2 are exemplified as technologies for measuring received signal qualities at a plurality of locations in a service area in a mobile communication system and determining a pattern for disposing base stations based on a result of the measurement.    [Patent Document 1] JP-A 2000-333239    [Patent Document 2] JP-A 2001-285923